In addition to the more "standard" Individual interior options, you can get other items. All these pictures are from the M3 of "Mark's M." Original thread here.
Picture #1 - Additional leather pieces (center console, shift boot and brake handle in rust brown).
Picture #2 - Piano black interior trim with the "///M" logo lasered into it.
Picture #3 - Floor mats with colored piping.

A picture from the M3 of "Technic." He got Jerez Black exterior and Rust Brown interior. He also added the new M Performance steering wheel with bicolor leather, the center console in color-coded Rust Brown to match the extended leather (instead of default black-colored plastic), and the handbrake boot in Rust Brown.